Film drying apparatus have been employed to dry photosensitive film after completion of a wet developing process in conventional photographic developing systems. The photosensitive film is transported through the film drying apparatus by a transport mechanism that includes a plurality of rollers. The rollers guide the photosensitive film past a plurality of air tubes or chambers, each of which includes a longitudinal air discharge port. The air tube is generally made gradually smaller from an inlet end, through which drying air is supplied to an opposite closed end or exhaust end in an attempt to make the air flow uniform across the length of the discharge port.
It is particularly desirable to provide a uniform flow of drying air in both magnitude and direction to insure that the photosensitive film is properly dried. Inconsistent or uneven air flow can cause portions of the photosensitive film to be overexposed or underexposed to the drying air, which can lead to problems such as variations in film gloss (defined as the measure of specularity or directionality of the surface reflection), either as excessive gloss or patterns such as stripes or spots of differing gloss. Accordingly, a vector field representing the desired uniform flow of air from the discharge port would ideally consist of a plurality of parallel vectors perpendicular to the discharge port that are of uniform length.
It has been found, however, that conventional air tubes allow a non-uniformity in flow direction and magnitude along the length of the air tube as air progresses from the tube inlet and is forced to make a right angle turn to exit the discharge port. The air supplied to the air tube is under pressure and wants to take the path of least resistance. The air will therefore want to exit the discharge port at an angle. In addition, the highest velocity pressure will also be at the far end of the air tube away from the tube inlet, which produces non-uniformities that produce irregular drying patterns on the photosensitive film.
In view of the above, it is an object of the invention to provide an air tube for use in a film drying apparatus that produces a uniform output air flow, in both magnitude and direction, in order to maximize drying efficiency.